1. Field of the Invention
The present invention illustrates a network system and a method for establishing data link, and more particularly, the network system for establishing data link by using relay node under a peer to peer network.
2. Description of the Prior Art
With advancement of network techniques, a real-time based data transmission and a real-time based data broadcasting mechanism can be accomplished by using a wired or a wireless network. In general, data communication by using the network follows a specific or a standard protocol of the network. Nowadays, several protocols of the network are introduced for establishing a wireless link, such as a file transfer protocol (FTP), a transmission control/internet protocol (TCP/IP), and a peer to peer (P2P) protocol. Specifically, the peer to peer protocol belongs to a node-based data exchange mechanism. The advantage of the P2P protocol is to reduce amount of nodes connected by a P2P transmission path. Thus, P2P-based transmission can reduce a rate of packet loss and a risk of information leakage.
In a conventional P2P network, when a node A establishes a P2P-based data link to a node B, the node A executes a login process to a P2P server or transmits a request of connection to the P2P server. Then, the node A provides information of unique identifier (UID) of the node B to the P2P server. By doing so, the P2P server can acquire connection or link information between the node A and the node B. Then, the P2P server transmits an internet protocol address of the node B to the node A. Thus, the node A can establish a data link to the node B for achieving P2P-based data transmission. For example, the node A can establish a data link to the node B by using a technique of P2P hole punching. After the data link is established, data transmission (i.e., for example, data packets transmission) between the node A and the node B can be performed.
However, in a standard network system, each node satisfies one of the three configurations. As known, the three configurations include a network address translation type 1 (NAT Type-1), a network address translation type 2 (NAT Type-2), and a network address translation type 3 (NAT Type-3). Specifically, the NAT Type-3 belongs to a symmetric configuration. When the node A and the node B satisfy a configuration of NAT Type-3, a P2P-based data link between the node A and the node B cannot be established directly due to restrictions of the NAT Type-3. In other words, link failure between two arbitrary nodes may be occurred in conventional P2P network.